The Gatehouse website record of a licence to crenellate for Whittington Castle granted on 1221 [probably June or later]

Rex R. Com Cestr et Linc salutem. Sciatis quid linam dedimus Fulcoi fit Warini castrum suum de Witintun competenter firmare que idem Fulco nobis pepigit et manucepit per carta suam qoud nobis per castrum illud nullatenus mesfaciet ita quod debite nobis fidei transgressor efficiatre. Et ideo vob mandamus quod ipsum Fulcone praedictum castrus praedicto modo firmare promittatis. T. H. etc. ut supra secunda pro eunder.
Eode modo scribitre Vic. Salop. (Rot. Litt. Claus.)

Rex R. Com Cestr et Linc salutem. Mandumus Vobis rogates quatinus prosonaliter si fieri potest eatis ad castrum de Witintun vel tales loco vestro de quibus bene comfidatis illuc mittatis ad videndus opracoem casti illius et qualiter fermetre . et si firmetre sic quod possit defendi concessa Waleses. non promittatis tunc quod amplier nec aliter firmeter. Si vero tale non freuit quod non possit defendi contra Waleses tunc non promittatis quod aliter firmeter quam firmat erat ante guerra T. ut supra secunda (Rot. ob. et fin.)

(These are crude transcriptions of the Record Commission transcriptions which uses a number of none standard letter forms and accents to reflect the hand and abbreviations of the original scribe. Gatehouse has attempted to expand the abbreviations but is not a Latin scholar - If an accurate transcription is required reference should be made to the Record Commission.)

Granted at Salop [Shrewsbury].

Comments

King writes "A licence was not normally required in this part of the country, but the owner, Fulk fitz Warin II, was a suspect character; he was permitted to build (firmare) his castle, but next year the King is found giving orders that the castle was not to be stronger, or otherwise built, than for defence against the Welsh; if it could not be defended against them, it was to be returned to the state it had been in before the war; i.e. presumably that of a defenceless earthwork (Rot. Lit. Claus., i, 520b)"
It should be noted these are Close, not Patent, Roll entries and, therefore, not actually a licence to crenellate in the strictest sense.

Original source is;

Hardy, D.H. (ed), 1833), Rotuli Litterarum Clausarum in Turri Londinensi asservati (Record Commission) Vol. 1 p. 460a, p. 520b
Hardy, D.H. (ed), 1835, Rotuli de oblatis et finibus in Turri Londinensi asservati, tempore Regis Johannis (Record Commission) p. 224

(In fact, the original source given is usually a transcription/translation of what are precious medieval documents not readily availably. It should be noted that these transcription/translations often date to the nineteenth or early twentieth centuries and that unwitting bias of transcribers may affect the translation. Care should also be taken to avoid giving modern meaning to the medieval use of certain stock words and terms. Licentia is best translated as 'freedom to' not 'permission'.)

Significant later sources are;

King, D.J.C., 1983, Castellarium Anglicanum (London: Kraus) Vol. 2 p. 439n97
Coulson, Charles, 1993 Aug, 'Specimens of Freedom to Crenellate by Licence' Fortress: The castles and fortifications quarterly Vol. 18 p. 3-15

Fulk Fitz Warine (b. 1170)

Born in 1170, Fulk Fitz Warine (also spelled 'Warin' and 'Waryn') was brought up as a companion to the royal children, including Henry II's son John. There was bad blood between Fulk and John, and as they grew older, they became enemies. In 1197, the 27-year-old Fulk inherited Whittington Castle from his father. However, Sir Morys Fitz Roger coveted Whittington, and he turned to the king for help. John – who ascended the throne in 1199 – gave the castle and its lands to Morys. Fulk protested and his brother John struck Sir Morys between the eyes. Trumped-up charges of treason were made and Fitz Warine and his companions were outlawed. For three years, they operated a guerrilla campaign in the forests along the Welsh border. (Channel 4 - In the footsteps of Robin Hood)

The tenurial history of Whittington was complex in the late C12/ early C13. Warine was granted a market charter in 1221, shortly before the crenellation licence, and may well have been establishing his claim to the manor. The castle was able to withstand a siege by Llewellyn the Great suggesting the castle was complete by 1223, which, in turn, suggests much of the work must have been commenced before 1221. How much the later codex to the licence was aimed at appeasing Llewellyn, rather than controlling Warine, is an interesting question.

Biographical source include;

Wright, Thomas, 1855, The History of Fulk Fitz Warine (London) online copy